Key trade officials of the United States, Europe, Japan, and Canada met over the weekend at Key Biscayne, Fla., and promised to avoid new protectionist moves that would set up a "chain reaction."

There was no formal communique, and a commitment to consult with each other was couched in very general language. Moreover, the pressing trade issues facing the world were discussed in a multilateral, rather than a bilateral context.

Thus, there was no discussion of the U.S. complaint that Canada is discriminating against U.S. investment, or U.S. companies' lawsuits contending that European companies have been "dumping" steel here at an unfair price.

Instead, at the suggestion of U.S. Trade Ambassador William Brock, the trade officials met informally at the Florida resort for two days of nonspecific discussion of worldwide trade issues. In two private sessions, at lunch, and on the golf-course, they had a chance to sound each other out on the different national perspectives.

One of the participants, Canadian Trade Minister Edward C. Lumley, said in a telephone interview from Key Biscayne yesterday that "the next six to 12 months--especially the next six--are going to be the most difficult for all our economies. Therefore, the problem for most of us is how best to manage this period, in resisting protectionist pressures."

He said that in a period of recession and low growth now faced by most of the industrialized world, it is tempting to try to solve jobs problems at home by blocking imports. "But if we do that, we're all losers," Lumley said.

He praised Brock for calling the meeting, and for setting the tone. "In the past, there has been little effort to be sensitive to each other's problems," Lumley said. He concluded that the result of the Key Biscayne meeting will be increased sensitivity of each country to the others' problems.

Shintaro Abe, Japanese minister of international trade and industry, conceded "there is some room for improvement on the part of Japan in the area of nontariff barriers." These restrictions, including standards for safety, have been widely criticized by European and American manufacturers as a thinly disguised way of keeping foreign goods out of the Japanese market.

Abe, who arrrived in Washington yesterday for a round of talks with Reagan administration officials, said a review of his country's nontariff barriers should be completed by the end of this month. "I expect drastic improvement" in that area, he added.

But other officials took a wait-and-see attitude on Abe's promise that Japanese nontariff barriers would be lowered. The Common Market participants, Sir Roy Denman and Wilhelm Haverkamp, appeared to be most skeptical, noting that the Japanese had made similar promises before.

Abe also reportedly urged that the industrial countries do something to retard the spread of nontariff barriers in the "advancing" industrial countries such as Brazil and Mexico.

Brock told a news conference the two-day session had not produced any trade agreements or policy breakthroughs, but that there was a solid commitment to avoid restrictive actions. "The proof of the pudding will come in the next several months, but I think we have made a very good beginning," he declared.

On multilateral problems, Brock told his opposite numbers that the United States is seeking a general understanding that there should be no discrimination against investments, and other services, as there is in trade.

Steel was discussed only in the sense that Brock explained to the Common Market representatives the attitude of U.S. companies on dumping by foreign steelmakers, while Abe expressed Japan's dismay that the "trigger price mechanism"--which had provided a floor under U.S. import prices--was threatened by the U.S. companies' challenge to the European companies.